Hi,

I found out that calling eventtarget.removeEventListener doesn't remove the Eventlistener so it's being garbage collected. 

If you run this code:
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Worker.State;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.web.WebView;
import javafx.stage.Stage;

import org.w3c.dom.events.Event;
import org.w3c.dom.events.EventListener;
import org.w3c.dom.events.EventTarget;

public class WebViewTest extends Application{

	private Scene scene;	
	private Pane top;
	private Pane bottom;
	private EventListener listener;

	public static void main(String[] args) throws Exception {
		launch(args);
	}

	@Override
	public void start(Stage primaryStage) throws Exception {

		primaryStage.setScene(new Scene(new BorderPane()));
		scene = primaryStage.getScene();
		top = new HBox();
		((BorderPane)scene.getRoot()).setTop(top);
		bottom = new HBox();
		((BorderPane)scene.getRoot()).setBottom(bottom);
		addWebView();
		Button but = new Button();
		but.setText("add and remove eventlistener");
		but.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				addWebView();				
			}
		});
		bottom.getChildren().add(but);
		primaryStage.show();

	}

	public void addWebView() {
		top.getChildren().clear();
		final WebView webView = new WebView();
		top.getChildren().add(webView);
		webView.getEngine().loadContent("HELLO");
		listener = new EventListener() {

			@Override
			public void handleEvent(Event evt) {
			}
		};
		webView.getEngine().getLoadWorker().stateProperty().addListener(new ChangeListener<State>() {

			@Override
			public void changed(ObservableValue<? extends State> arg0, State arg1, State arg2) {
				if (arg2 == State.SUCCEEDED) {
					EventTarget target = (EventTarget) webView.getEngine().getDocument().getDocumentElement();
					target.addEventListener("keydown",listener , false);
					webView.getEngine().getLoadWorker().stateProperty().removeListener(this);
					target.removeEventListener("keydown",listener , false);
					listener = null;
				}

			}
		});
	}
}

And clicking on the button for example 10 times, then when you look in for example JProfiler, so can see 10 instances of EventListenerImpl, and it never decreases.. Isn't this a bug?

Best regards
Troels